1. Technical Field of the Invention
The present invention relates to methods and hardware in the field of graphics processing, and, in particular, to the rasterizing of triangles.
2. Description of Related Art
In graphics accelerator chips used in, for example, personal computers (PCs), it is desirable to reduce as far as possible the number of pixels for which textures are retrieved from texture memory. One way this can be reduced is to include a step during rasterization of individual pixels within a predetermined area, representing a screen or the forming a sub-part of a screen, to ascertain whether each pixel being scanned is within a triangle being rasterized. Only those pixels that are within a triangle being rasterized have texture and color mapping performed on them, thereby reducing the load on the texture memory bandwidth.
While this is a desirable procedure in principle, checking whether a given pixel is within a triangle is not a trivial matter, and the resultant calculations can drastically increase the load on the graphics chip central processing unit (CPU). This is exacerbated by the fact that all triangles in a given area need to be tested.
There is accordingly a need for a method and apparatus that ascertains, with reduced processor load, whether a pixel is within a triangle defined in relation to an area.